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How come there is visible light in Uv lights?

  1. Sep 10, 2010 #1
    Hi!
    I did a laboration on detecting different wavelenght from a UV-c light tube and the electrometer detected some activity from the Monochromator in the area of visible light (400nm-700nm).
    I would like to know if this has something to do with the quality of the light tube? Or does something happen between the light tube and Monochromator that gives some photons less energy, ie collisions in the path to the Monochromator?

    Or is it a combination of both?

    Also, how come we see the " glow " (the purple glow ) of a UV light, it should not be visible for our eyes. What I mean is, shouldnt the Uv light bulb look like a regular bulb that is not connected to any power source like this one http://www.rapidonline.com/netalogue/zoomed/Large/M077725W01.jpg" [Broken]

    Thanks!
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 10, 2010 #2
    I think it's from the bulb, but it depends on what type of bulb exactly.

    If it was from the air, wouldn't the ratio of uv intensity vs visible intensity change with distance?
     
  4. Sep 11, 2010 #3
    A typical UV-C lamp is a "naked" (quartz glass, no phosphors, no filters) low pressure mercury discharge. Mercury has quite a few spectral lines in the visible range, so what you measure is completely normal. There is probably some Neon/Helium/Argon in the tube to help start the discharge. This will add a few visible spectral lines.
    The "black light" lamp in your link has all visible light filtered out; check this http://en.wikipedia.org/wiki/Black_light

    maimonides

    Take care of your eyes and skin when working with UV-C!
     
  5. Sep 11, 2010 #4
    Thanks maimonides for your reply, it helped me understand a little bit more about the visibile light emitted from the UV-c light tube.
     
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